Support microsecond timestamp format (#1426)

Adds microsecond timestamp support.

https://github.com/grafana/loki/issues/1407

docs/clients/promtail/configuration.md

@@ -410,7 +410,7 @@ timestamp:
   # Determines how to parse the time string. Can use
   # pre-defined formats by name: [ANSIC UnixDate RubyDate RFC822
   # RFC822Z RFC850 RFC1123 RFC1123Z RFC3339 RFC3339Nano Unix
-  # UnixMs UnixNs].
+  # UnixMs UnixUs UnixNs].
   format: <string>
 
   # IANA Timezone Database string.

docs/clients/promtail/stages/timestamp.md

@@ -14,7 +14,7 @@ timestamp:
   # Determines how to parse the time string. Can use
   # pre-defined formats by name: [ANSIC UnixDate RubyDate RFC822
   # RFC822Z RFC850 RFC1123 RFC1123Z RFC3339 RFC3339Nano Unix
-  # UnixMs UnixNs].
+  # UnixMs UnixUs UnixNs].
   format: <string>
 
   # IANA Timezone Database string.
@@ -46,6 +46,7 @@ Additionally, support for common Unix timestamps is supported with the following
 
 - `Unix`: `1562708916`
 - `UnixMs`: `1562708916414`
+- `UnixUs`: `1562708916414123`
 - `UnixNs`: `1562708916000000123`
 
 Custom formats are passed directly to the layout parameter in Go's

pkg/logentry/stages/timestamp.go

@@ -26,6 +26,7 @@ const (
 
 	Unix   = "Unix"
 	UnixMs = "UnixMs"
+	UnixUs = "UnixUs"
 	UnixNs = "UnixNs"
 
 	TimestampActionOnFailureSkip    = "skip"

pkg/logentry/stages/timestamp_test.go

@@ -203,6 +203,17 @@ func TestTimestampStage_Process(t *testing.T) {
 			},
 			time.Date(2019, 7, 9, 21, 48, 36, 414*1000000, time.UTC),
 		},
+		"unix microsecond success": {
+			TimestampConfig{
+				Source: "ts",
+				Format: "UnixUs",
+			},
+			map[string]interface{}{
+				"somethigelse": "notimportant",
+				"ts":           "1562708916414123",
+			},
+			time.Date(2019, 7, 9, 21, 48, 36, 414123*1000, time.UTC),
+		},
 		"unix nano success": {
 			TimestampConfig{
 				Source: "ts",

pkg/logentry/stages/util.go

@@ -78,6 +78,14 @@ func convertDateLayout(predef string, location *time.Location) parser {
 			}
 			return time.Unix(0, i*int64(time.Millisecond)), nil
 		}
+	case "UnixUs":
+		return func(t string) (time.Time, error) {
+			i, err := strconv.ParseInt(t, 10, 64)
+			if err != nil {
+				return time.Time{}, err
+			}
+			return time.Unix(0, i*int64(time.Microsecond)), nil
+		}
 	case "UnixNs":
 		return func(t string) (time.Time, error) {
 			i, err := strconv.ParseInt(t, 10, 64)